International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 04, April 2019, pp. 695–700, Article ID: IJCIET_10_04_073
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJCIET&VType=10&IType=4
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
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MODERNIZATION OF HYDRAULIC MODES OF
HEATING NETWORKS IN TYUMEN
A V Yemelyanov, V V Ilyin, T S Zhilina
Industrial University of Tyumen, Volodarskogo, 38, Tyumen, Russia, 652000
ABSTRACT
The article presents a proposal for solving the problem of excessive temperature of
the return line based on the results of the study of the hydraulic modes of heat
networks from the Tyumen CHP-2. The authors propose a modernized scheme of a
group heating point (GHP), which is installed at the border of the balance of the main
and district heating network. For this scheme, a physico-mathematical model is
created, the purpose of which is to derive a modernized formula for the mixing ratio
for a GHP, with which it is possible to determine the necessary actions to increase the
efficiency of heat supply system control and the amount of time required for this. The
calculation is made for the existing heat chambers of the city of Tyumen using the
GHP scheme, the results of which revealed certain patterns.
Key words: energy efficiency of the heat supply system, group heating point, main
and distribution heat network, mixing ratio.
Cite this Article: A V Yemelyanov, V V Ilyin, T S Zhilina, Modernization of
Hydraulic Modes of Heating Networks in Tyumen, International Journal of Civil
Engineering and Technology 10(4), 2019, pp. 695–700.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=4
1. INTRODUCTION
Currently, the main problem of centralized heat supply in the Russian Federation is the
imbalance of the heating network, which over the years impairs the hydraulic stability of heat
supply systems. In particular, it is observed in populous cities with very extensive and ―hardto-control" heat supply systems.
Conducting a study to identify the factors that reduce the energy efficiency of centralized
heat supply using the example of main heating networks in the circuit of the Tyumen CHP-2
[1] has become a task the solution of which will ensure uninterrupted operation of heat supply
systems.
The main factor that reduces the energy efficiency of centralised heat supply in the city of
Tyumen is a significant deviation from the norm in terms of flow rate and return temperature.
Moreover, excessive flow rate is directly related to excessive temperature of the return
pipeline, since this deviation from the norm leads to an increase in the heat carrier flow rate,
otherwise the heat carrier parameters are reduced, and the consumer does not get the amount
of heat necessary for a comfortable stay in the room.
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A V Yemelyanov, V V Ilyin, T S Zhilina
2. MATERIALS AND METHODS
To solve the problem of the increased return temperature, a control scheme was proposed with
the participation of a group heating point (hereinafter referred to as the GHP) located on the
border of the balance sheet attribution between the main and distribution heat network. So,
having considered the existing GHP scheme, a modernized scheme was proposed (Figure 1)
with the possibility of more efficient control of the main parameters of heat supply. In the
existing GHP schemes [2] in the form of a temperature controller, a two-way regulating
device is used, but for more efficient heat distribution it is proposed to use a three-way
regulating device, with installation of pumping equipment on the return heat pipeline.
Thus, it is proposed to create a method for calculating the amount of return heat carrier
from the return heat pipeline to the supply one through the use of a three-way regulating
device at the GHP.
Figure 1 GHP scheme:
1,6,4,9 – locking device; 2 – downstream pressure regulator;
3- three-way control valve; 5 – controller; 7 – upstream pressure regulator;
8 – pump; 10 – check valve; 11 – temperature sensor on the supply pipe of the main
heating network; 12 – temperature sensor on the return pipe of the main heating network; 13 –
temperature sensor on the supply pipe of the main heating network; 14 - ball valve with
manual reconfiguration function.
The essence of the modelling process is to derive a pattern of changes in the parameters of
heat relative to the control modes in the considered period of time. The model will show
exactly what actions need to be taken to increase the efficiency of control and how long it will
take to stabilize the temperature and heat process.
The possibility of deriving regularities of the control process with respect to time is
proposed to be realized thanks to the derivation of a coefficient that will fully reflect the
mutual influence of changes in parameters during qualitative and quantitative control.
The main parameters in the regulation are flow, pressure and temperature. The flow rate
and pressure characterize the capacity of the heat network, and the flow rate and temperature
mode characterize the heat load, so it was decided to use the heat balance formula and the
capacity of control devices [3].
The factual and calculated structure of the division of heating networks between the main
and district heating networks is presented in Figures 2 and 3.
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Modernization of Hydraulic Modes of Heating Networks in Tyumen
Figure 2. The existing distribution structure of the main and district heating networks
Figure 3. Design scheme for the use of the GHP in a physico-mathematical model:
Where - normalized flow rate of the main heating network, - factual flow rate of the
main heating network,
- normalized heat load for the main heating network,
- factual
heat load for the main heating network,
- normalized flow rate of the district heating
network,
- factual flow rate of the district heating network,
- normalized heat load for
the district heating network,
- factual heat load for the district heating network,
normalized supply and return heat carrier temperature for the main heating network,
factual supply and return heat carrier temperature for the main heating network,
,
factual supply and return heat carrier temperature for the district heating network, ΔPd1-Apressure loss at the three-way valve of port A, ΔPd1-B- pressure loss at the three-way valve of
port B, ΔPd2- pressure loss at the manual valve, – - factual heat flow rate for make-up.
It should be noted that when introducing a modernized control scheme, the main
parameters of the heat carrier must be divided into factual and normalized (nominal). In case
of deviations, the control process begins, in which the make-up of the supply heat line is
performed from the return one.
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3. RESULTS AND DISCUSSION
The purpose of the algorithm for calculating the physical and mathematical model is to
calculate the mixing ratio considering the existing flow rates of the heat carrier and pressure
losses at the three-way valve. To do this, we determine the maximum heat flow rate
which is necessary for district heating networks to obtain the normalized heat load
without
considering mixing.
From the formula of heat balance, we get:
((
) , kg/s
)
(1)
where
- normalized heat load for the district heating network, kW;
- factual
supply and return heat carrier temperature for the main heating network C; C - specific heat
of the heat carrier in the temperature range
, kJ/(kg·ºC).
Since the calculation is carried out without considering mixing, we assume that:
and
, whereas
and
Therefore:
(2)
The amount of make-up heat flow rate for admixing:
, kg/s
(3)
Pressure loss at the three-way and manual control valves will be expressed from the
formula of the capacity of control devices [3]
(
)
, bar
(4)
where - water flow rate through the valve, m3/h;
- valve capacity, (m3/h)/bar0.5
To calculate the mixing ratio in the control mode, it is necessary to calculate the flow rate
depending on the capacity and pressure loss at the control device. Figure 3 demonstrates that
port A shows the factual flow rate of the main heating network . Port B shows the make-up
rate Gmuf which, when mixed with
, compensates for the normalized heat load .
necessary for the district heating network. The resulting flow rate during mixing will be
factual ( ). To obtain a modernized formula, the formula for the mixing ratio (for the heat
carrier flow rate) [4] and the transformed formula 4 were taken:
√
(5)
√
where
- pressure loss at the port B three-way valve, bar;
- pressure loss at
the port A three-way valve, bar; KVS-A- normalized capacity of the port A three-way valve,
m3/h; KVS-B- normalized capacity of the port B three-way valve, m3/h.
To simplify the calculation of the mixing ratio in the nominal valve operation mode, it is
necessary to clarify that the nominal capacity is obtained as a result of factory tests, which
take place when creating resistance of 1 bar on a control device [3], therefore
and
values are subject to reduction and the final formula for the nominal mixing ratio will
be:
(6)
Comparing formulas 4, 6 and the flow design scheme of the heat carrier in the mixing
modes (Figure 3), we obtain the formula for the factual mixing ratio µf which determines the
ratio of water admixture at the mixing point of the supply and return heat carrier.
(
√
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) (
√
698
)
(7)
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Modernization of Hydraulic Modes of Heating Networks in Tyumen
where
- pressure loss at the port B three-way valve, bar;
- pressure loss at
the port A three-way valve, bar;
- pressure loss at the manual valve, bar.
Having obtained the exact value of the mixing ratio, we can determine the temperature
of the supply heat carrier regarding µ. For this, it is necessary to derive the
value from the
formula of the mixing ratio (according to the heat carrier temperature) [4], which in this case
is equal to , and the value of =
and =
, then the desired formula will be:
(
)
, °C
(8)
In this case, the temperature of the return main heating network t2n will be equal to the
factual temperature of the return heating network t2f.
The temperature value t1f of the supply heat line makes it possible to determine the heat
load that can be obtained by admixing. This value will be below the norm, as there is a
decrease in the temperature difference between the supply and return heat lines, therefore, to
determine the time to reduce the heat load, you need to know the factual flow rate that can be
supplied in the GHP control mode. For this, you need to calculate the amount of heat left not
consumed by the end user because of which there is an excess of the return heat carrier
temperature.
The formula for calculating the unused amount of heat is:
(
)
,kW
(9)
where
- normalized return heat carrier temperature for the main heating network,
°C; - return heat carrier temperature for the main heating network, °C; - heat flow rate in
the main heating network; c- heat capacity equal to 4.187, kJ/kg ·°C.
It should be noted that
and
.
In formula 9, the temperature mode was taken based on the physical movement of the heat
carrier from the return heat line to the supply one (Figure 2). The flow rate of heat return to
the supply line will be calculated based on the heat balance formula and will be:
((
)
) , kg/s
(10)
where
- supply main heating network temperature, °C.
Initially, it is necessary to determine how much heat can be returned from the return heat
line to the supply one. This value will be the heat flow rate from the superheated return heat
line Gsuperheating. In turn, Gsuperheating is determined based on the heat load
Qsuperheating, which is in the flow rate of the heating network Gn.
In this regard, the superheated flow rate Gsuperheating will affect the make-up heat flow
rate Gmu, which in fact will go to feed into the supply heat line for admixing and will be able
to take this effect into account and is the factual flow rate of the supply heat line from the
return heat carrier to the supply heat line Gmu.f.
, kg/s
(11)
The factual heat flow rate for the make-up Gmu.f may be negative. This is because the
flow rate from the superheated heat carrier may not be enough, and this will affect the heat
flow rate that goes into the heating network.
Note that Gmu.f will show the possibility of effective redistribution of the heat flow from
the superheated return heat carrier to the supply one. This value can be either positive or
negative. In this regard, for negative values of Gmu.f, the formula for determining the factual
flow rate Gf*(*) will be:
, kg/s
(12)
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For positive values of Gmu.f, the formula will be:
, kg/s
(13)
For general physical modelling, the time factor over which the superheating of the
return heat carrier will be eliminated is of great importance. The formula for calculating the
time spent on eliminating superheating, based on the formula of heat balance, and considering
the number of hours of operation, has the form:
(
(
)
), h
(14)
During the time of operation of the heat exchanger (n), a decrease in the heat load below
the normalized one will be observed; therefore such control is possible during the night time
when the heat load on the hot water system will be minimal.
4. CONCLUSIONS
1. The current norms regulating the calculation of the heat losses of buildings, taking into
account the single ventilation of heated rooms, have caused a situation in which the design
heat capacity of heating systems exceeds the actual requirements of buildings in the heat
energy for heating.
2. If the parameters of the heating network are oriented towards a European approach to
apartment ventilation, there is no need to raise the maximum temperature of the heat carrier to
a virtually unrealistic design value of 150 °C. For a satisfactory heat supply, 124 °C would be
sufficient.
3. The technical specifications for heat supply must be designed in such a way that they
strictly regulate the real obligations of the buyer and seller of the thermal energy and stimulate
its rational use while maintaining the existing hydraulic conditions of the network.
4. Maintaining the first comfort condition in residential buildings while meeting energy
efficiency requirements can be achieved by combining sanitary and hygienic requirements
and reducing energy parameters.
REFERENCES
[1]
SP 54.13330.2011 Multi-apartment residential buildings. Updated version of SNiP 31-012003. - Moscow: Ministry of Regional Development of Russia, 2012.
[2]
Taschenbuch fur Heizung+Klimatechnik 97/98.
[3]
ASHRAE Standard 62-1999. Ventilation for Acceptable Indoor Quality.
[4]
Gershkovich, V. F. Mold on the walls. German lesson. News of heat supply. 1(17), 2002.
[5]
Sokolov, E. Ya. Central heating and heating networks. Moscow: Energoizdat, 1982.
[6]
Chistovich, A. S. The concept of development of central heating systems. Heat and energy
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[7]
TR AVOK-4-2008. Technical recommendations on the organization of air exchange in the
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[8]
Sukhanova, K. I., Ilyin, V. V. Technical and economic calculation of thermal insulation
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— URL https://moluch.ru/archive/143/40178
[9]
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